VD/VDR

Vitamin D is a secosteroidalprohormone, it can be synthesized at sufficient levels in skin, given adequate skin exposure to UV B radiation from sunlight. Vitamin D modulates its biological effects by directly regulating target gene expression through the Vitamin D receptor (VDR), a ligand-regulated transcription factor and a member of the nuclear receptor superfamily. Whether synthesized in the skin or ingested, vitamin D requires two hydroxylation steps to become the biologically active hormone, 1,25-dyhydroxyvitamin D3 [1,25(OH)2D3], a form that signals through the VDR. The hormone-bound VDR modulates target gene transcription in response to vitamin D. VDR acts as a master transcriptional regulator of autophagy. Activation of the VDR by vitamin D induces autophagy and an autophagic transcriptional signature in breast cancer (BC) cells.

There are 2 forms of vitamin D. Vitamin D2 (ergocalciferol) comes from irradiation of the yeast and plant sterol ergosterol, and vitamin D3 (cholecalciferol) is found in oily fish and cod liver oil and is made in the skin. Vitamin D represents vitamin D2 and vitamin D3.

VDR agonist 1 (compound 28) is a nonsteroidal Vitamin D receptor (VDR) agonist, with an IC50 of 690 nM in MCF-7 cells. VDR agonist 1 arrests the cell cycle through the up-regulation of p21 and p27, promotes apoptosis by increasing the expression of BAX and decrease the expression of Bcl-2.

24, 25-Dihydroxy VD3 is a compound which is closely related to 1,25-dihydroxyvitamin D3, the active form of vitamin D3, but like vitamin D3 itself and 25-hydroxyvitamin D3 is inactive as a hormone both in vitro and in vivo.